The present invention generally relates to industrial control systems and in particular to a system and method for testing the functionality of industrial control modules.
Industrial controllers are special purpose computers used for controlling factory automation devices. Under the direction of a stored program, a processor of the industrial controller examines a series of inputs reflecting the status of a controlled processor or device and changes outputs affecting control of the controlled process or device. The inputs and outputs may be of an analog or digital nature. Generally industrial controllers are constructed in modular fashion to accommodate different application requiring different numbers and types of input/output (I/O) circuits as is determined by the particular device or process being controlled. In such modular systems, a number of different functional modules connect together through a common backplane in a rack to share data and power. However, other types of modules forming industrial controller solutions include communication modules adapted to provide communication links, counter/encoder modules for monitoring motor position information, programming modules adapted to be programmable to function according to a user""s instructions, relay modules typically provided to shut off automated devices and control modules adapted to control and operate industrial control modules.
Prior to the introduction of industrial control modules into a factory environment, the modules are tested by a test system to verify the proper operation and functionality of the industrial control module. Typical test systems employed to test industrial control modules suffer from several deficiencies. For example, high current type relays are employed for coupling the modules to input and output stimulus devices to verify the operation of independent inputs and outputs of the industrial control modules. Furthermore, low current low resistance relays are employed to couple measurement instruments to these devices to measure the outputs of the industrial control modules. typically, the high current relays are disposed on a relay board with one end of each relay coupled to a backplane. The backplane is then coupled to the input and output stimulus devices through additional relays. The other end of the relay is provided for coupling to the industrial control module input and output signals. If one of the relays fail, the entire relay board must be repaired or replaced. The exact relay that has failed on the relay board is very difficult to determine and board replacement and repair is very expensive.
The low current relays are also disposed on a relay board with one end of each relay coupled to a backplane. The backplane is then coupled to the measurement instruments through additional relays. The other end of the relay is provided for coupling to the industrial control module input and output signals. In addition to having the aforementioned repair problems, the low current relays are subjected to measurement errors for low voltage signals during signal measurements due to the additional resistance of the wiring and the relays from the instruments to the backplane, from the backplane to the relays and from the relays to the units under test. An adjustment factor found by trial and error is typically added to the allowable device limits to compensate for the additional resistance. However, due to wear in the relay contacts from time and development errors this adjustment factor may change over time. The result is production failures, which requires additional production and engineering manpower costs.
The conventional test systems utilized for testing industrial control modules sometimes employ an electronic load to simulate current drawing systems that the industrial control module will drive. Therefore, the electronic load is coupled and decoupled to each output of the industrial control module one at a time and then measured using an appropriate measurement device for both low current and high current testing. After the electronic load is coupled to an output, the load will need to stabilize before it can be measured. This constant moving and stabilizing of the electronic load is time consuming and limits the ability of the industrial control module to be completely tested at a reasonable test time.
Therefore, it is apparent that there is an unmet need for a test system and method that mitigates the aforementioned deficiencies.
The present invention provides for a system and method for testing industrial control modules. Input and output stimulus signals, communication lines, measurement device lines and relay contacts are provided at a tester interface panel. This allows for a test developer to configure the relay contacts in any way that the developer desires to provide appropriate connections of stimulus, communications and measurements for a given industrial control module. The switching of the relays between a normally closed position and a normally open position can be controlled by output modules coupled to a computer. Preferably, the relays are insertable and releasable in a socket for easy fault isolation and replacement. Furthermore, the same relays or similar relays can be employed for both low current measurements and high power stimulus.
In one aspect of the invention, a test fixture is provided for interfacing with the tester interface panel and a unit under test. The test fixture provides mechanical and electrical connections to a family of industrial control modules. A personality module is also provided that is coupleable to the test fixture and provides mechanical and electrical connections to different industrial control modules of a family of industrial control modules. This allows for utilization of a single fixture for testing a family of industrial control modules with a much simpler and less expensive personality module being provided for each industrial control module type.
One particular aspect of the invention relates to a system for testing industrial control modules having at least one input. The system comprises a tester interface panel and an input stimulus device coupled to the tester interface panel. The input stimulus device is adapted to provide at least one input stimulus signal. At least one relay is provided and includes a normally open contact, a common contact, and a normally closed contact coupled to the tester interface panel. The at least one relay is configurable to couple the at least one input stimulus signal to the at least one input.
Another aspect of the present invention relates to a system for testing industrial control modules having at least one output signal. The system comprises a tester interface panel and a measurement instrument coupled to the tester interface panel. The measurement instrument is adapted to measure the at least one output signal. An electronic load device is also provided. Additionally, at least one power relay is provided including a normally open contact, a common contact, and a normally closed contact coupled to the tester interface panel. At least one analog relay including a normally open contact, a common contact, and a normally closed contact is also coupled to the tester interface panel. The at least one power relay is configurable to couple the electronic load to the at least one output signal and the at least one analog relay is configurable to couple the measurement instrument to the at least one output signal.
Another aspect of the present invention relates to a system for testing industrial control modules having at least one of a plurality of inputs and a plurality of outputs. The system comprises a tester interface panel and an input stimulus device, an electronic load and a measurement instrument all coupled to the tester interface panel. The input stimulus device is adapted to provide a plurality of input stimulus signals and the measurement instrument is adapted to measure the at least one of a plurality of inputs and a plurality of outputs. A plurality of power relays are provided with each including a normally open contact, a common contact, and a normally closed contact coupled to the tester interface panel. A plurality of analog relays are also provided with each including a normally open contact, a common contact, and a normally closed contact coupled to the tester interface panel. Any of the plurality of power relays are configurable to couple one of the electronic load and any of the plurality of input stimulus signals to any of the at least one of a plurality of inputs and a plurality of outputs and any of the plurality of analog relays are configurable to couple the measurement instrument to any of the at least one of a plurality of inputs and a plurality of outputs.
Yet another aspect of the present invention relates to a method for testing industrial control modules having at least one of an input and an output. The method comprises the steps of providing a tester interface panel, coupling input stimulus signals, output stimulus signals, measurement instrument lines and relay contacts to the tester interface panel where the relay contacts including a normally open contact, a common contact, and a normally closed contact for each relay coupled to the tester interface panel. The method also includes the steps of configuring at least one relay of the each relay coupled to the tester interface panel, so that at least one of the input stimulus signals, output stimulus signals and measurement instrument lines are coupleable to the at least one of an input and an output. A control system is provided for moving the at least one relay between a normally closed state and a normally open state for coupling the at least one of the input stimulus signals, output stimulus signals and measurement instrument lines to the at least one of an input and an output.
Still yet another aspect of the present invention relates to a system for testing industrial control modules having at least one of an input and an output. The system comprises means for providing accessibility to input stimulus signals, output stimulus signals, measurement instrument lines and relay contacts where the relay contacts include a normally open contact, a common contact, and a normally closed contact for each relay. The system further comprises means for configuring at least one relay of the each relay, so that at least one of the input stimulus signals, output stimulus signals and measurement instrument lines are coupleable to the at least one of an input and an output. The system also includes means for moving the at least one relay between a normally closed state and a normally open state for coupling the at least one of the input stimulus signals, output stimulus signals and measurement instrument lines to the at least one of an input and an output.